MPE actions: update

Third LHC Splice Review, November 12-14, 2012

Rüdiger Schmidt, TE-MPE reporting for …..

• Circuit Documentation: S.Pemberton, K.Pereira

• Splice Resistance Measurements on DFBXs: R.Mompo, G.d’Angelo, M.Bednarek

• Circuit Modelling: A.Verweij, B.Auchmann, Z.Charifoulline, D.Molnar, D.E.Rasmussen, E.Ravaioli, H.Riihimaki S.Rowan,

+ many others

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MPE actions from last review and circuits screening

Second LHC Splice Review, November 28-30, 2011

Rüdiger Schmidt, TE-MPE reporting for …..

R.Mompo, G.d’Angelo, M.Bednarek, N.Catalan-Lasheras

A.Verweij, E.Ravaioli, S.Rowan, D.Molnar

K.Dahlerup-Petersen, M.Zerlauth

S.Pemberton, K.Pereira

A.Ballarino, H.Thiesen, A.Siemko

+ others

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2011

2011: Overview Magnets Electrical Circuits Screening

1. Information on magnet and powering system

2. Electrical and thermodynamic modelling of the magnets / circuits

3. HV testing – K.Dahlerup-Petersen

4. Issues related to cold diodes – F.Savary

5. Related to CSCM - Wednesday

6. Others

7. Not discussed

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Nr Circuits Short description Main Responsible1 All Information library MPE2 All Electrical integration drawings MPE3 All Peak DC voltage check MPE

4 AllE-model (e.g. PSPICE), transient voltage, effects of faults MPE

5 All Hot spot temperature MPE 6 All Ground insulation current monitor EPC7 All Periodic automatic test of insulation MPE8 All Protection resistors for V taps MPE / MSC9 All In-situ test plan for circuits not tested to full load MPE

10 All Test simultaneously main and corrector circuits MPE

11 RB Diodes: qualify design or engineer repair solution MPE / MSC12 RB/RQ Internal voids in T connection to diodes MPE13 RB/RQ Improve spider insulation MSC14 RB/RQ Consolidate main splices MSC

15 RQ Diodes: qualify design or engineer better solution 16 17 IT Define repair plan MSC18 IT Test & document splices MPE19 6kA Quench studies MPE20 Cur Leads Redundant temperature sensors in safety chain CRG / MPE21 Cur Leads Top temperature sensors in safety chain CRG / MPE22 Cur Leads Risk of electrical breakdown due to He leaks MSC23 DFB Repair 13kA splices or prove them healthy MSC / MPE24 DFB BB deflection studies MSC

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LHC Electrical Drawings: Status

S.Pemberton

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Status

All 8 sectors were graphically complete by the end of 2011.

Each sector has been internally verified against all our gathered data (EDMS Drawings, Procedures, etc) and the XML circuit definition from the Layout Database.

This labor intensive process lasted many months but now enables us to be confident in the accuracy of the drawings.

All individual cell drawings have been exported into DWFx format then uploaded onto the Electrical Drawings Navigator. This allows people to view and manipulate the drawings without having to install AutoCAD on their PC.

Due to recent changes in the AutoCad plug-in: new users are experiencing difficulties viewing the drawings, currently being addressed.

Potential users should become aware of the availability of the drawings and user instructions will be provided.

There should be a period of general use by different groups to establish any underlying problems concerning the usability of the navigator.

We would value any feedback as to the legibility of the drawings and would eventually be happy to perform any upgrades.

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Drawings for electrical circuits (S.Pemberton & K.Pereira)

Future work and comments

– Adding of QPS signals: would make the drawing unreadable, better to include information on separate drawings

– Non – conformities: still to be added after starting to use the drawings

– Also required for addressing quench propagation: variation of cooling conditions due to different insulation (number of layers of insulation), helium conditions (liquid at 1.9K or 4.3K, gaseous) – to be defined how to do it

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Navigator Screen Shots

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ISRM project

DFBXs Splice measurements

Richard Mompo on behalf of ELQA team8

Splice Resistance Measurements on DFBXs

• There are eight DFBXs in the LHC. Four have an additional D1 magnet connected.

• Two measuring set-up were prepared in order to measure two DFBXs at a time.

• Measurements took place at the end of the Xmas break during the powering phase.

• Circuits RQX/RTQX2 were powered together with a Mexican pyramid.

• Use of standard power cycle “PNO.D11” with 3 current plateaus reduced to 10 min. each (instead of 1h).

• D1 magnets were measured separately using of standard cycle power “PNO.c2”

Overview

DFBX Layout in LHC

During PNO.D11, RTQX1 power converter is OFF.

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Q2 is seeing 9700 Amps!

Cycle with voltage measurements

Number of splices in DFBX

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D1 splices belong to another family and should be compared to other IPDs

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assuming that all splices are identical!

DVM3 and DVM7 of DFBXB.R1 are slightly outside of the Gaussian curve

Conclusions

• All eight DFBXs during 2011-2012 were measured during the Xmas break.

• Q1, Q2a, Q2b and Q3 internal splices (splices between poles) were not measured

• Nominal resistance value for the two groups of splices:– Around 0.5 E-09 Ohms for Q1, Q2 and Q3 splices – Around 1 E-09 Ohms for D1 splices (comparable with other IPDs magnets)

• An internal note similar to the one written for IPDs and IPQs is (https://edms.cern.ch/document/1250924/1)

Circuit modeling

Software Used for Description

QP3 ConductorIn-house Fortran code, especially developed for electro-thermal calculations of 1D conductors with helium cooling.

Roxie MagnetIn-house Fortran code, especially developed for field optimization of accelerator magnets.

PSpice Circuit Commercial software for the electrical modeling of entire circuits.

COMSOL Specific parts

Commercial multiphysics modeling and engineering simulation software.

We mainly use the following simulation software:

Arjan Verweij

Performed simulations/studies using QP3

Type of simulation Circuit / magnet

Hot spot calculations 600 A bus, 600 A magnet, 6 kA bus

BLM threshold study 6 kA MQM, MBRB, MB, MQ, MQTLH

QPS threshold study 6 kA MQM & bus

Quench propagation study RB & RQ magnet, RB and RQ bus, 13 kA pigtail

Bus protection for defective joints RB & RQ bus

Simulation of the 2008 accident RB bus

Temperature increase in the interlayer splice MB

Safe current in case of a defective interpole joint

MB

Safe current for a defective bus joint in LHe and GHe. Joint with and without shunt.

RB and RQ, incl. magnet, bus and diode

Simulation of experimental tests on joints Several tests in FRESCA, Q8-Q9 test in SM18

CSCM for 4-5 TeV and & TeV validation, for various types of current cycles

RB and RQ

Arjan Verweij

Roxie

Code for the electromagnetic simulation and optimization of accelerator magnets

Field maps, field errors, AC losses, magnetization. Models available for all LHC magnets.

2D and 3D quench simulation with discretization of a few cm. Possibility for heater firing, beam losses, cooling, and quench back. Models available and validated for MB and MQ. Quench models for a few other magnets will be made soon.

Output often used as input in QP3 / PSpice / Comsol.

Arjan Verweij

PSpice

Electrical modeling of entire circuits, including PC, leads, ground, magnets, switches, etc.- Circuits with thousands of elements are simulated rather

quickly.

- Effective thermal modeling is included (e.g. resistive built-up of a quenching magnet) but needs input from other programs. Possibility to discretize a magnet in several parts.

- RB, RQ, RQX, RD2, RQ4, RQ10, RQS, RQTL, RQTD/F, RCBY models are done. For each model, the simulations of a Fast Power Abort and a quench (training and/or heater induced) are compared to experimental data from the machine.

- Any other circuit can be quickly modeled if needed, starting from one of the existing models

Arjan Verweij

Circuit Special studies / Failure cases

RB

Effect of delay in switch opening. Effect of snubber capacitor (including short-to-ground).

Effect of PC configuration (additional resistor, inversion of crowbar and filter in PC). Effect of earthing point position.

Effect of AC behaviour of magnet. Effect of unbalanced apertures on the QPS detection.

Simulation of AUG event of 14/5/2011. Short circuit to ground.

RQXShort circuit to ground.

Non-opening of a thyristor.Opening of FWD during ramp down.

RQ4Short circuit to ground.

Non-firing of quench heater.Inter-turn short.

RQTD/F Quench-back. Lack of parallel resistance. Decrease of the EE resistance.

RCBYH Inter-turn short.

CSCMEffect of spread in diode opening voltage.

Effect of the use of 0, 1, or 2 EE's.Non-opening of a by-pass diode.

PSpice

Arjan Verweij

COMSOL

Multiphysics modeling and engineering simulation software

Thermo-electrical modeling of specific parts of circuits requiring 3-D approach, such as shunts on 13 kA joints, bolted ‘half-moon’ connection to diode, ‘praying hands’ 6 kA joints, current leads, etc.

Model of the 13 kA joint is ready (RB & RQ, shunted & non-shunted). EDMS report under approval.

Model of the dipole and quad diode is ready including the diode leads and contacts. Model is partially validated using SM18 measurements. Cooling to LHe and GHe is included.

Model of a HTS ‘sandwich’ is under development.

If needed, a realistic model of the 6 kA and/or 13 kA current leads can be made. Arjan Verweij

Conclusion

During the last year we have largely increased our expertise of thermo-electrical modeling of (parts of) the LHC circuits.

One of the Roxie experts has joined our section, so that we now have experts for the conductor, magnet, and circuit modeling.

The COMSOL models have been transferred last year from a technical student to a staff member (and another technical student), so as to guarantee long term know-how in this field.

We will focus next year on having validated quench models of most types of magnet, and incorporation of effective quench models in the circuit models. This is important to be prepared for the larger number of (normal and beam-induced) quenches expected after LS1.

Arjan Verweij

Reserve

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